With the increasing emphasis on expedited “overnight” shipments, the number and volume of air cargo shipments is increasing. Some aircraft used for air cargo shipments are configured to transport only cargo, while other aircraft are configured to transport both passengers and cargo.
Typically, items being shipped by air are first loaded onto specially configured pallets or into specially configured containers. In the airfreight industry, these various pallets and containers are commonly referred to as Unit Load Devices (“ULDs”). ULDs are available in various sizes, shapes and capacities, and typically bear external markings that identify their type, maximum gross weight, tare weight, and other pertinent information.
A ULD typically is loaded with cargo at a location that is distant from the immediate vicinity of an aircraft. Once a ULD is loaded with cargo items, the ULD is weighed, transferred to the aircraft, and is loaded onto an aircraft through a doorway or hatch using a conveyor ramp, scissor lift, or the like. Once inside the aircraft, a ULD is moved about the cargo compartment until it reaches a final stowage position. Multiple ULDs are brought onboard the aircraft, and each is placed in its respective stowed position.
Various types of aircraft that are used to exclusively transport cargo have variously arranged cargo compartments for receiving and stowing ULDs. As shown in FIGS. 1 and 2, a typical large cargo aircraft 10 includes a forward cargo compartment 12a and an aft cargo compartment 12b located beneath the aircraft's main deck 16, and within the aircraft's “lower lobe.” These cargo compartments commonly are referred to as the “forward lower lobe” 12a and the “aft lower lobe” 12b, respectively. In addition to forward and aft lower lobes 12a, 12b, a typical large cargo aircraft 10 often is equipped to receive and stow ULDs 18 on its main deck 16 in a main deck cargo compartment 14. A cargo aircraft 10 may be loaded with ULDs of various types, shapes, and sizes. As shown in FIG. 2, spaces or gaps typically exist between and around at least some adjacent ULDs 18 in their stowed positions.
To facilitate movement of a ULD within an aircraft cargo compartment as the ULD is loaded, stowed, and unloaded, the deck of an aircraft cargo compartment typically includes a number of raised roller elements. These roller elements often include elongated roller trays that extend longitudinally along the length of the cargo deck, ball panel units, and the like. For example, roller trays typically include elongated rows of cylindrical rollers that extend in a fore and aft direction. Ball panel units include plates with upwardly protruding spherical balls. The ULDs sit atop these roller elements, and the roller elements facilitate rolling movement of the ULDs within the cargo compartment. Cargo decks also commonly are equipped with one or more power drive units (PDUs). PDUs are electrically powered rollers that can be selectively raised above the roller elements, and selectively energized to propel a ULD across a cargo deck in a desired direction. One example of a PDU is described in U.S. Pat. No. 6,834,758 to Goodrich Corporation. Some PDUs may be equipped with one or more sensors for detecting the presence or absence of a ULD directly above the PDU. An example of one such ULD-sensing PDU is described in co-pending U.S. patent application Ser. No. 11/469,643 filed Sep. 1, 2006, and assigned to Goodrich Corporation.
Typically, a person responsible for loading or unloading ULDs selectively controls operation of an aircraft's PDUs from a master cargo control panel 20, like that shown in FIG. 3. Typically, such a master cargo control panel 20 typically is located at a convenient location near the doorway of an aircraft's main deck and/or lower cargo deck. An aircraft may also be equipped with one or more local cargo control panels 30 like that shown in FIG. 4. The control panels 20, 30 are configured to permit a person to selectively raise and engage one or more PDUs with a pre-positioned ULD, and to selectively activate the PDU to propel the ULD in a forward or aft direction within a cargo compartment.
Once a ULD is moved to its final stowed position, the ULD must be restrained against both vertical and lateral movement during flight. Accordingly, the deck and sidewalls of a cargo compartment typically include a plurality of restraint devices that selectively engage the stowed ULD, and keep the ULD stationary. One example of such a restraint is a latch that is removably fixed to the floor, and is selectively movable between a deployed (latched) position and a retracted (unlatched) position. In the deployed position, an engaging member of the latch is upright, and protrudes above the upper surface of the roller elements. In the retracted position, the engaging member is recessed below the upper surface of the roller elements such that the engaging member will not interfere with movement of a ULD passing overhead. The engaging member can be manually moved between its deployed and retracted. Such restraint latches are known in the art, and are commercially available in various types and sizes. The restraint latches are positioned at predetermined “install points” on a cargo deck. Such install points coincide with deck locations having features for receiving and retaining a restraint latch, such as recesses, holes, slots, pins, cutouts, or the like. One example of an install point is a recess between upwardly extending rails of a roller track recessed within a cargo deck. Installation points also commonly are provided along side rails on sidewalls of the cargo compartments.
A typical aircraft cargo deck may include several hundred install points. However, for a given cargo configuration, not all install points are populated with restraints due to weight and cost considerations. For example, on a cargo deck having about eight hundred total install points, only about three hundred of the install points may require restraints. Usually, an aircraft operator will consider the types and sizes of ULDs that are likely to be required for a particular load configuration, and will install the appropriate number of restraints before cargo loading according to such projections.
Each ULD normally requires multiple restraint devices, and different types of ULDs require different numbers of restraints. Operational criteria for each ULD specify the required number, type and locations of restraints based on a ULDs maximum gross weight. Such operational criteria also specify a reduced maximum gross weight for situations where one or more of the required restraints are missing or otherwise unavailable. Thus, on a given flight, if one of several restraints to be used to secure a ULD is damaged or missing, that ULD may still be transported in the chosen position, but only if it meets the reduced maximum gross weight specification.
The number of ULDs, the types of ULDs to be transported, and the weight of each ULD often vary between flights. Care must be taken when loading aircraft with cargo to ensure that the final weight and balance of the aircraft is acceptable. An aircraft's performance and handling characteristics are affected by the aircraft's gross weight and its effective center of gravity. An overloaded or improperly balanced aircraft will require more power and greater fuel consumption during flight, and the aircraft's stability and controllability may be affected.
Before ULDs are loaded onto an aircraft, a person in charge of the loading activities (hereinafter the “load master”) develops a desired load configuration that contemplates the aircraft's weight and balance criteria, and the number, types and weights of the ULDs to be loaded. The load configuration defines where each of the ULDs should be located on a cargo deck. In its simplest form, a load configuration can be a two-column list that includes a first column identifying each ULD, and a second column identifying a desired stowed position for each ULD.
Typically, a loading crew tasked with loading an aircraft receives a printed copy of the loadmaster's load configuration. In order to ensure that each ULDs operational restraint requirements are satisfied, ground crew members ensure that restraints of the correct type are installed at the various install points required by the load configuration. Often, a loading crewmember tasked with configuring restraints according to a given loading configuration must rely on his familiarity with various ULDs, restraints, and cargo deck equipment. The loading crewmember also may be assisted by color-coded markings on the cargo deck that designate install points and the like. The loading crewmember performs a visual inspection, and determines whether operable restraints of the correct types are installed at the correct install points for each ULD to be loaded onto the aircraft.
During inspection, a loading crewmember may discover a missing, damaged, or inoperable restraint. In such a case, the crewmember typically reports such findings to the loadmaster, who then may check the ULD operational criteria to determine whether a ULD with a lighter weight or of a different type might be relocated to an affected ULD location. Sometimes, a restraint may be moved from one install point to another install point having a missing or damaged restraint, such that restraint requirements for all ULDs ultimately are satisfied.
In order to assist air cargo loading crews, automated cargo loading systems have been developed. One such automated cargo loading system is described in published U.S. Pat. No. 7,198,227, assigned to Goodrich Corporation, which is hereby incorporated by reference. The described system is configured to automatically identify, track, and report the positions of ULDs within an aircraft in real time, thereby permitting a person who is remote from loaded ULDs to monitor the current status of loading or unloading activities. In such a system, each ULD may include a machine-readable wireless tag that includes identification information and other information specific to a particular ULD. Local and long range wireless tag readers positioned at various points within an aircraft can be used to identify the presence and specific real-time location of any ULD that is onboard an aircraft. Such a system can include one or more remote visual displays that present visual representations of the real-time locations of each ULD.
In rare instances, as ULDs are loaded and unloaded from an aircraft, the ULDs and/or their contents can be subject to unauthorized tampering, theft, vandalism, and the like. More frequently, the ULDs and/or their contents can be damaged during loading or unloading activities, or during transport. Such unauthorized activities and/or damage can be costly to air cargo carriers. Commonly, such unauthorized activities and/or damage may not be discovered until after a ULD reaches its destination. In addition, the cause or source of damage, theft, tampering, or vandalism to a ULD and/or its contents may not be apparent or discoverable once the damage, theft, tampering, or vandalism is discovered. In addition, an aircraft's cargo compartment and ULDs can sometimes be used by unauthorized persons to smuggle illicit items and materials.
Accordingly, there is a need for a system and method for surveying, monitoring, and recording activities and events that occur within an aircraft's cargo compartments, especially during loading and unloading activities. Preferably, such a system and method will assist air cargo carriers in determining the causes and/or sources of cargo tampering or damage, and will establish an evidentiary record of such activities and events. In addition, such a system and method preferably will be compatible with other onboard cargo loading and logistics systems, and even more preferably, will be integrated with such other onboard cargo systems.